linux-kernel - Re: [PATCHv5 4/4] ARM: mx51: Add support for low power suspend on MX51

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Message-ID: <20110323102405.GG29521@pengutronix.de>
Date:	Wed, 23 Mar 2011 11:24:05 +0100
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Dinh.Nguyen@...escale.com
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux@....linux.org.uk, u.kleine-koenig@...gutronix.de,
	arnaud.patard@...-net.org, ra5478@...escale.com,
	xiao-lizhang@...escale.com, festevam@...il.com
Subject: Re: [PATCHv5 4/4] ARM: mx51: Add support for low power suspend on
 MX51

On Mon, Mar 21, 2011 at 04:30:38PM -0500, Dinh.Nguyen@...escale.com wrote:
> From: Dinh Nguyen <Dinh.Nguyen@...escale.com>
> 
> Adds initial low power suspend functionality to MX51.
> Supports "mem" and "standby" modes.
> 
> Tested on mx51-babbage.
> 
> Signed-off-by: Dinh Nguyen <Dinh.Nguyen@...escale.com>
> ---
>  arch/arm/mach-mx5/Makefile   |    1 +
>  arch/arm/mach-mx5/pm-imx51.c |   74 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 75 insertions(+), 0 deletions(-)
>  create mode 100644 arch/arm/mach-mx5/pm-imx51.c
> 
> diff --git a/arch/arm/mach-mx5/Makefile b/arch/arm/mach-mx5/Makefile
> index 0b9338c..787cb80 100644
> --- a/arch/arm/mach-mx5/Makefile
> +++ b/arch/arm/mach-mx5/Makefile
> @@ -6,6 +6,7 @@
>  obj-y   := cpu.o mm.o clock-mx51-mx53.o devices.o ehci.o system.o
>  obj-$(CONFIG_SOC_IMX50) += mm-mx50.o
>  
> +obj-$(CONFIG_PM) += pm-imx51.o
>  obj-$(CONFIG_CPU_FREQ_IMX)    += cpu_op-mx51.o
>  obj-$(CONFIG_MACH_MX51_BABBAGE) += board-mx51_babbage.o
>  obj-$(CONFIG_MACH_MX51_3DS) += board-mx51_3ds.o
> diff --git a/arch/arm/mach-mx5/pm-imx51.c b/arch/arm/mach-mx5/pm-imx51.c
> new file mode 100644
> index 0000000..f5164b2
> --- /dev/null
> +++ b/arch/arm/mach-mx5/pm-imx51.c
> @@ -0,0 +1,74 @@
> +/*
> + *  Copyright (C) 2011 Freescale Semiconductor, Inc. All Rights Reserved.
> + *
> + * The code contained herein is licensed under the GNU General Public
> + * License. You may obtain a copy of the GNU General Public License
> + * Version 2 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/gpl-license.html
> + * http://www.gnu.org/copyleft/gpl.html
> + */
> +#include <linux/suspend.h>
> +#include <linux/clk.h>
> +#include <linux/io.h>
> +#include <asm/cacheflush.h>
> +#include <asm/tlbflush.h>
> +#include <mach/system.h>
> +#include "crm_regs.h"
> +
> +static struct clk *gpc_dvfs_clk;
> +
> +static int mx5_suspend_enter(suspend_state_t state)

Either the name of the file or the name of this function is wrong. You
should decide for imx5 or imx51.

> +{
> +	if (gpc_dvfs_clk == NULL)
> +		gpc_dvfs_clk = clk_get(NULL, "gpc_dvfs");
> +
> +	if (gpc_dvfs_clk) {
> +		clk_enable(gpc_dvfs_clk);
> +		switch (state) {
> +		case PM_SUSPEND_MEM:
> +			mx5_cpu_lp_set(STOP_POWER_OFF);
> +			break;
> +		case PM_SUSPEND_STANDBY:
> +			mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
> +
> +		if (state == PM_SUSPEND_MEM) {
> +			local_flush_tlb_all();
> +			flush_cache_all();
> +
> +			/*clear the EMPGC0/1 bits */
> +			__raw_writel(0, MXC_SRPG_EMPGC0_SRPGCR);
> +			__raw_writel(0, MXC_SRPG_EMPGC1_SRPGCR);
> +		}
> +		cpu_do_idle();
> +		clk_disable(gpc_dvfs_clk);
> +	}else {
> +		printk(KERN_ERR "Cannot enter SRPG suspend -no gpc_dvfs clock!\n");
> +		return -EPERM;
> +	}
> +
> +	return 0;
> +}
> +
> +static int mx5_pm_valid(suspend_state_t state)
> +{
> +	return (state > PM_SUSPEND_ON && state <= PM_SUSPEND_MAX);
> +}
> +
> +static const struct platform_suspend_ops mx5_suspend_ops = {
> +	.valid = mx5_pm_valid,
> +	.enter = mx5_suspend_enter,
> +};
> +
> +static int __init mx5_pm_init(void)
> +{

You should call clk_get here. Then you don't have to do the test for the
clock over and over again and can print the warning only once. Also, NULL
can be a valid clock. Please use IS_ERR().

Sascha

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